Location Filtering Using Mobile Country Code

ABSTRACT

Methods, program products, and systems for location filtering using mobile country code (MCC) is described. A mobile device can determine its geographic location using locations of access points of a wireless communications network to which the mobile device is connected. The mobile device can wirelessly receive identifiers of one or more access points of the wireless communications network and a current MCC through a cellular network. The mobile device can identify a polygon that is a bounding box of a geographic area that corresponds to the current MCC. The mobile device can select a set of access point locations from a location database using the received identifiers, where the access point locations are inside the identified polygon. The mobile device can determine a current location of the mobile device based on an average location of the selected set of access point locations.

TECHNICAL FIELD

This disclosure relates generally to determining a geographic locationof a mobile device.

BACKGROUND

Various technologies can be employed in a wireless communicationsnetwork to allow mobile devices to communicate with each other and withdevices on a wired network. Depending on the technologies used,communication distances of the mobile devices can range from a fewmeters (e.g., in a Personal Area Network) to several kilometers (e.g.,in a cellular network). Among the wireless communications technologies,a wireless local network (WLAN) can include a local area network (e.g.,a computer network covering a relatively small physical area, like ahome, office, or a small group of buildings such as a school) that usesradio waves for communication. Some examples of WLAN technology includeWiFi, which can include any WLAN products that are based on anyInstitute of Electrical and Electronics Engineers (IEEE) 802.xxstandards. A mobile device can communicate with other devices in theWLAN or with devices outside the WLAN through an access point of thewireless network.

In general, a cellular communications network can allow mobile devicesto communicate with each other or with other devices over longerdistances than those of a WLAN. Some example cellular technologiesinclude a Global System for Mobile communications (GSM) network, or aUniversal Mobile Telecommunications System (UMTS) network. A mobiledevice in the cellular network at a given location can have a currentmobile country code (MCC) that can designate a country of the givenlocation, a current mobile network code (MNC) that can identify a mobilenetwork operator, a current location area code (LAC) that can identify alocation area (which can be defined by the mobile network operator), anda current time zone of the location. The MCC, MNC, LAC, and current timezone information can be provided by the mobile network operator to themobile device through a cellular tower.

SUMMARY

Methods, program products, and systems for location filtering usingmobile country code (MCC) are described. A mobile device can determineits geographic location using locations of access points of a wirelesscommunications network to which the mobile device is connected. Themobile device can wirelessly receive identifiers of one or more accesspoints of the wireless communications network and a current MCC througha cellular network. The mobile device can identify a polygon that is abounding box of a geographic area that corresponds to the current MCC.The mobile device can select a set of access point locations from alocation database using the received identifiers, where the access pointlocations are inside the identified polygon. The mobile device candetermine a current location of the mobile device based on an averagelocation of the selected set of access point locations.

Techniques for location filtering using mobile country code can beimplemented to achieve the following exemplary advantages. A mobiledevice can determine its location even though the mobile device isincapable of receiving Global Positioning System (GPS) signals. Forexample, the mobile device that is not equipped with or coupled to a GPSreceiver can determine a current location of the mobile device. Themobile device can determine its location when the mobile device isconnected to a wireless network (e.g., WiFi, WiMax, or other wirelessnetwork). The mobile device can determine its location based onlocations of wireless access points to which the mobile device canconnect. GPS-enabled mobile devices can also take advantage of thelocations of wireless access points when, for example, GPS signals areweak (e.g., inside buildings).

Location filtering using MCC can offer an efficient way to filter outaccess points that are recently moved. If a mobile device has a locationrecord of an access point to which the mobile device is connected, andthe location record indicates that the access point is located incountry that is different from the current country, the mobile devicecan exclude the access point from the location calculation. The mobiledevice can avoid inaccurate location calculation when, for example, anaccess point to which the mobile device is connected to is located inCanada but the mobile device has a record indicating the access point islocated in France. Location calculation can be more accurate whentechniques of location filtering using MCC are employed.

The details of one or more implementations of location filtering usingMCC are set forth in the accompanying drawings and the descriptionbelow. Other features, aspects, and advantages of determining locationsof wireless access points will become apparent from the description, thedrawings, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an overview of location filtering using mobile country code.

FIG. 2A is an overview of techniques of determining locations ofwireless access points.

FIG. 2B illustrates determining locations of wireless access points in athree-dimensional space.

FIGS. 3A-3C illustrate exemplary stages of determining locationsassociated with access points in WLAN using mobile devices.

FIG. 3D illustrates an exemplary stage of determining locationsassociated with access points in WLAN using mobile devices in athree-dimensional space.

FIGS. 4A and 4B are flowcharts illustrating exemplary processes ofdetermining locations associated with access points in WLAN using mobiledevices.

FIG. 4C is a block diagram illustrating an exemplary system implementingtechniques of determining locations of wireless access points.

FIG. 5A illustrates techniques for determining locations of mobiledevices using techniques of determining locations of wireless accesspoints.

FIG. 5B is a flowchart illustrating an exemplary process of locationfiltering using mobile country code.

FIG. 5C is a flowchart illustrating an exemplary process of determininga location of a mobile device using filtered locations of wirelessaccess points.

FIG. 6 illustrates an exemplary user interface for determining locationsof mobile devices using locations of wireless access points.

FIG. 7 is a block diagram of an exemplary architecture of a mobiledevice.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION Overview of Location Filtering Using Mobile CountryCode

FIG. 1 is an overview of location filtering using mobile country code(MCC). For convenience, only North America and Hawaiian Islands areshown in FIG. 1. Further more, only Canada, United States, and Mexicoare given as examples for location filtering using MCC. The techniquesof location filtering using MCC is applicable for other countries andcontinents.

Mobile device 112 can connect to a wireless communications networkthrough access point 125. Access points 125 can include a hardwiredevice or computer software that can act as a communication hub forwireless devices to connect to a wired network. Multiple access points125 can be distributed in an area (e.g., an office building or anairport). Access point 125 can be associated with a location whereaccess point 125 can serve. For example, access point 125 a can belocated in San Francisco, Calif., U.S.A., and serves a certain area(e.g., a building located at 300 Bush Street).

Mobile device 112 can use a location of access point 125 to which mobiledevice 112 is connected to determine a current location of mobile device112. When mobile device 112 is wirelessly connected to access point 125a, mobile device 112 can identify the location of access point 115 afrom a location database. The location database can store an identifier(e.g., a Media Access Control (MAC) address) of access point 115 a andthe location associated with the identifier. For example, the record inthe location database can associate the identifier of access point 125 awith latitude and longitude coordinates 37°47′27.56″N and122°24′08.69″W, indicating that access point 125 a is located at 300Bush Street, San Francisco, Calif., U.S.A. Mobile device 112, knowingthe identifier of access point 115 a because mobile device 112 iswirelessly connected to access point 115 a, can determine that, at leastat time of connection, mobile device 112 is located in San Francisco,Calif., U.S.A. More details of determining the location of access point125 and the current location of mobile device 112 will be describedbelow.

Access point 125 can be mobile. For example, access point 125 a canphysically move from San Francisco, Calif., U.S.A. to Edmonton, Alberta,Canada (e.g., due to company relocation). Moved access point 125 a isrepresented as access point 125 b. However, unless and until thelocation database is updated, the location database still associates theidentifier that identifies the actual hardware component of access point125 b as San Francisco, Calif., U.S.A. Therefore, mobile device 114,currently connected to mobile device 125 b located in Edmonton, Alberta,Canada, may incorrectly determine that mobile device 114 b is located inSan Francisco, Calif., U.S.A.

One way to avoid the incorrect location determination is to use acurrent MCC of mobile device 114 to filter the location database. An MCCis a code that the International Telecommunication Union (ITU) assignedto a country. The MCC is unique for each country and can be used toidentify the country. Each country can have one or more MCC assigned toit. Table 1 illustrates some example MCCs and corresponding countries.

TABLE 1 Exemplary MCCs MCC Country 302 Canada 310-316 United States ofAmerica 334 Mexico

Mobile device 114 can have a subscriber MCC that can identify a countryof a subscriber of mobile device 114. The subscriber MCC can indicate ahome country of mobile device 114. For example, the subscriber mobiledevice 114 can be “334,” indicating the home country of mobile device113 is Mexico. Additionally, mobile device 114 can detect a current MCCindicating in which country mobile devices 114 is currently located. Forexample, the current MCC of mobile device 114 can be “302,” indicatingthat mobile device 114 is currently located in Canada. The current MCCof mobile device 114 can be obtained from a specialized processor ofmobile device 114 that is responsible for wireless communications andcontrol. In various implementations, the specialized processors can beknown as baseband processors, GMS wireless modems, and UMTS wirelessmodems. In this specification, unless otherwise specified, the term MCCwill be used to refer to the current MCC of a mobile device rather thanthe home MCC of the mobile device.

Mobile device 114 can use the current MCC to filter the locationdatabase by determining whether a record in the location database isconsistent with the current MCC. For example, mobile device 114 candetermine that access point 125 b, having a location that corresponds toSan Francisco, Calif., United States, does not match the current MCC“302” which indicates that the current country is Canada. Because SanFrancisco is not located in Canada, mobile device 114 can determine thatthe record for access point 125 b in the location database is incorrect,and remove the record from the database.

To determine whether the location of access point 125 b is consistentwith the current MCC, a system can generate polygons that are boundingboxes of each MCC and determine whether the location of access point 125b is inside the correct polygon. For example, bounding box 100 cancorrespond to MCC “302” (Canada). Bounding boxes 102 can correspond toMCCs “310,” “311,” “312,” “313,” “314,” “315,” and “316” (UnitedStates). Bounding box 104 can correspond to MCC “334” (Mexico). Forclarity, bounding boxes for other North American countries are not shownin FIG. 1. The location of access point 125 b, as recorded in thelocation database, can include a latitude and a longitude. For example,the record in the location database can associate the identifier ofaccess point 125 b with latitude and longitude coordinates 37°47′27.56″Nand 122°24′08.69″W, indicating that access point 125 b is located at 300Bush Street, San Francisco, Calif., U.S.A. This location is outside ofbounding box 100 for Canada. Therefore, mobile device 114 can remove therecord from the location database, and use another access point toestimate a current location of mobile device 114.

The system can use various algorithms to determine a bounding box (e.g.,bounding box 100) of a country associated with an MCC. A country (e.g.,Canada) can be represented as one or more simple polygons whose verticescan be stored in latitude/longitude coordinates. The bounding box of acountry can be a convex hull of the simple polygon of the countrydetermined by, for example, Akl-Toussaint heuristics or Melkman'sAlgorithm. In some implementations, a bounding box of a country can bedetermined by extreme points within the boundaries of the country (e.g.,easternmost, westernmost, northernmost, and southernmost points). Thebounding box can be a substantially rectangular area (e.g., boundingboxes 100, 102 and 104 on a map drawn using Mercator projection. Thebounding box can be stored using latitude/longitude coordinates of twopoints (e.g., its north-west vertex and its southeast vertex).

For example, bounding box 100 of Canada can have a northern boundarythat is delineated by latitude 83°08′N, corresponding to the latitude ofCape Columbia, Ellesmere Island, Nunavut, an extreme north point withinthe Canadian boundary. Bounding box 100 can have a southern boundarydelineated by latitude 41° 41′N, corresponding to the latitude of MiddleIsland, Ontario, an extreme southern point of Canada. Bounding box 100can have an eastern boundary delineated by longitude 52°37′W (CapeSpear, Newfoundland), and a western boundary delineated by longitude141°00′W (Yukon-Alaska border). Bounding box 100 can be stored in twosets of coordinates (e.g., 83°08′N/141°00′W and 41°41′N/52°37′W).

Some countries (e.g., the United States of America) can be representedas multiple simple polygons (e.g., 48 continental states, Alaska andHawaii). Countries that can be represented as multiple simple polygonscan have multiple bounding boxes (e.g., bounding boxes 102 a for Alaska,bounding box 102 b for continental 48 states, and bounding box 102 c forHawaii). Bounding boxes of various countries can overlap, as shown inthe overlapping areas between bounding boxes 100 and 102 a, for example.

Bounding boxes can be stored on a mobile device in association withMCCs. For example, mobile device 114 can store, or be connected to, ageographic database, in which MCCs and corresponding bounding boxes arestored. MCC “302” (Canada) can be associated with the north-west vertexand southeast vertex of bounding box 100, for instance.

When mobile device 114, whose current MCC is “302,” connects to accesspoint 125 b, and identifies a location of access point 125 b from thelocation database, mobile device 114 can compare the location againstbounding box 100 to determine whether the location is inside boundingbox 100. Various algorithms (e.g., ray casting algorithm or windingnumber algorithm) can be employed to determine whether the location isinside bounding box 100. For example, when bounding box 100 is expressedby the northwest vertex and southeast vertex, the latitude and longitudecoordinates of the location of access point 125 b can be compared to thelatitude and longitude coordinates of the vertices to determine whetherthe location of access point 125 b is located in the substantiallyrectangular area of bounding box 100.

Upon determining that the location of access point 125 b is insidebounding box 100 associated with current MCC “302,” mobile device 114can proceed to estimate a current location of mobile device 114 usingthe location of access point 125 b. If it is determined that thelocation of access point 125 b (e.g., 37°47′27.56″N and 122°24′08.69″W)is outside bounding box 100 (83°08′N/141°00′W and 41°41′N/52°37′W),mobile device 114 can use another access point within communicationrange to estimate the current location of mobile device 104. Mobiledevice 104 can also update the location database (e.g., by deleting therecord associated with access point 125 b marking the location of accesspoint 125 b as “dirty”). Thus, mobile device 114 can avoid displaying anincorrect current location.

Determining Locations of Wireless Access Points

FIG. 2A is an overview of techniques of determining locations ofwireless access points. For convenience, the techniques will bedescribed in reference to a system that implements the techniques ofdetermining locations of wireless access points.

A wireless local area network (WLAN) can be a radio communicationsnetwork that includes a number of access points 155. Access point 155can communicate with wireless devices (e.g., mobile devices 158 and 160)using various communication protocols. In some implementations, accesspoint 155 can be an access point of a WiFi™ network, which implements anInstitute of Electrical and Electronics Engineers (IEEE) 802.11-basedprotocol (e.g., IEEE 802.11a). In some implementations, access point 155can be an access point of a worldwide interoperability for microwaveaccess (WiMAX) network, which implements an IEEE 802.16 based protocol(e.g., IEEE 802.16-1554 or IEEE 802.16e-1555). Access point 155 can havea communication range that can reach from location of access point 155to anywhere from less than ten meters to several hundred meters,depending on factors including the configuration of access point 155 andphysical surroundings. Multiple wireless devices 158 and 160 can connectto an access point when mobile devices 158 and 160 are within thecommunication range of access point 155. In turn, multiple access points155 can be available to a single mobile device 158 or 160 forconnection. Mobile devices 158 and 160 can select a particular accesspoint 155 to which mobile devices 158 and 160 connect, based on variousfactors. For example, the selection can be based on whether mobiledevice 158 is authorized to connect to access point 155 a, or whetheraccess point 155 a can provide the strongest signal for the wirelessconnection to mobile devices 158.

The system can determine location areas 165 that are associated withaccess points 155. Location areas 165 can be calculated such that theyindicate where mobile devices 158 connected to access points 155 arelikely to be located. The system can make the determination based onknown locations from mobile devices 158 that are connected to accesspoints 155. Mobile devices 158 can be location-aware mobile devices, forexample, GPS-enabled mobile devices that have built-in, or be coupledwith, receivers that can receive Global Positioning System (GPS) signalsand determine locations using the GPS signals. Location-aware mobiledevices 158 are represented as black triangles in FIG. 2A. Whenlocation-aware mobile devices 158 are connected to a particular accesspoint 155 (e.g., access point 155 a), location-aware mobile devices 158can transmit the locations of the devices to access point 155 a. Accesspoint 155 a can relay the transmission, as well as an identifier ofaccess point 155 a, to the system. The system can determine an estimatedlocation area 165 a where any mobile device 158 or 160 connected toaccess point 155 a is most likely located. In this specification,estimated location areas 165 will be referred to as presence areas; toindicate that mobile device 158 or 160, when connected to a particularaccess point 155, is likely to be present.

To calculate presence areas 165, the system can apply an iterativeprocess (e.g., by performing a multi-pass analysis). The iterativeprocess can determine a presence area (e.g., presence area 165) that isassociated with an access point (e.g., access point 155) as a circle.The circle can have a center that corresponds to an average geographiclocation calculated based on locations of location-aware mobile devices158 that are wirelessly connected to access point 155. The circle canhave a radius that corresponds to an error margin, which can bedetermined by, for example, a distance between a location of a mobiledevice 158 and the average geographic location. Further details on theiterative process will be described below in reference to FIGS. 2 and 3.The iterative process can be executed periodically (e.g., every sixhours) to capture different wireless access usage patterns duringdifferent hours of a day as well as to capture potential moves of accesspoints 155.

The system can send information of presence areas 165 to mobile devices,including non-GPS-enabled mobile devices (e.g., mobile device 160), thatare connected to access points 155 such that the receiving mobiledevices can determine estimated locations of the devices using presenceareas 165. For example, if mobile device 160 is connected to accesspoint 155 b, the location of mobile device 160 can be estimated as tocoincide with presence area 165 b that is associated with access point155 b.

In a given area (e.g., an airport), numerous access points 155 canexist. Further more, as mobile device 160 can be mobile, it can belogical to send locations of access points that are not immediatelywithin a communication range of mobile device 160 but are close-byenough to mobile device 160, such that mobile device 160 can use thelocations to track its movement. To avoid sending a large amount oflocation data to mobile device 160, the system can filter access points155 and location areas 165 such that only the location data of a limitednumber of access points (e.g., access point 155 a), rather than locationdata of every single access point that exists in the world, aretransmitted. Filtering can be based on various factors, includingpopularity, stability, longevity, and freshness of locations 165 andaccess points 155.

To filter locations 165 and access points 155, the system can creategeographic grid 150 that contain cells 152. Cell 152 can be a polygonhaving a substantially rectangular shape, the polygon corresponding to ageographic area identifiable on geographic grid 150 by a latitude and alongitude of an identifying point of the geographic area (e.g., acenter, or a corner), and a size (e.g., a length measured in degrees oflongitude, and a width measured in degrees of latitude). Each cell 152can be used as a container that can contain a certain number oflocations. For example, cell 152 can be a rectangle whose length is0.0005 degrees meridian (approximately 56 meters) and whose width 0.0005degrees latitude (width in meters can vary depending on the latitude).Cell 152 can be configured to hold a number (e.g., three) of presenceareas 165 corresponding to access points 155. In some implementations,cell 152 can “hold” presence area 165 if the center of presence area 165is located within boundaries of cell 152. The presence areas 165 can beselected from all presence areas 165 that are located in cell 152 basedon one or more reliability factors. The selection can be based onvarious criteria such as popularity, stability, longevity, andfreshness.

A particular access point (e.g., access point 155 b) and the presencearea associated with the access point (e.g., presence area 165 b) neednot be located in a same cell 152. This can happen, for example, whenaccess point 155 b is located on a building in cell 152 a and mostmobile devices 158 connected to access point 155 b are located inanother building in cell 152 b. In some implementations, the system canignore the actual location of access point 155 b.

When mobile device 160 connects to an access point (e.g., access point155 a, whose associated presence area 165 a is located in cell 152 c),mobile device 160 can receive a location update from the system. Thelocation update can include all presence areas 165 that are located inthe same cell where presence area 165 a is located (e.g., cell 152 c).The location update can further include presence areas 165 that arelocated in other cells 152 (e.g., cell 152 a and cell 152 b) that areneighbors to cell 152 c on geographic grid 150.

When mobile device 160 connects to access point 155 a, mobile device 160can detect other access points 155 (e.g., access point 155 b) that areavailable. Mobile device 160 can identify presence areas (e.g., presenceareas 165 a and 165 b) for the available access points. Mobile device160 can calculate a current location of mobile device 160 using variousalgorithms. For example, when only one presence area 165 a isidentified, mobile device 160 can designate presence area 165 a as thecurrent location of mobile device 160. When two or more presence areas165 are identified, mobile device 160 can calculate its current locationusing an iterative process (e.g., a multi-pass analysis). The iterativeprocess can calculate an average location of the presence areas,calculate distances between the presence areas and the average location,and exclude presence areas that are the farthest away from the averagelocation. Mobile device 160 can repeat the iterations until a precisionrequirement is satisfied for determining a location of mobile device160. Mobile device 160 can designate the average location as a currentlocation of mobile device 160 and display the average location on a mapdisplay device.

In some implementations, the location update received on mobile device160 from the system can include numerous neighboring cells such that asufficiently large area (e.g., one or two square kilometers) aroundpresence area 165 a can be covered. Based on the location update thatcovers the large area, mobile device 160 can avoid having to requestfrequent updates when mobile device 160 moves. Mobile device 160 canhave opportunities to receive updated presence area information when,for example, mobile device 160 is idle or otherwise has availablecommunication bandwidth.

FIG. 2B illustrates determining locations of wireless access points in athree-dimensional space. Some location-aware mobile devices 158 (e.g.,GPS-enabled devices) can identify locations in a three-dimensionalspace. The locations can be represented by latitudes, longitudes, andaltitudes. Altitudes can be expressed, for example, as elevationmeasured in meters from sea level. Locating a mobile device in athree-dimensional space can be desirable when an altitude of the mobiledevice is necessary for locating the mobile device. For example,altitude can be used to determine on which floor the mobile device islocated in a high-rise building. Location of mobile device 158 inthree-dimensional space can be displayed on a two-dimensional map withthe elevation as an annotation, or on a three-dimensional map.

Mobile devices 158 can connect to access point 176. Mobile devices 158can be location-aware mobile devices that can transmit their locations,including latitude, longitude, and altitude coordinates to the system.The system can calculate an average location based on the latitude,longitude, and altitude coordinates received from mobile devices 158.Three-dimensional space 174, having the average location as a center andan error margin as a radius, can be associated with access point 176.Space 174 can represent a space that a mobile device is likely to belocated when the mobile device is connected to access point 176. In thisspecification, space 174 will be referred to as a presence space.

The system can send information on presence space 174 to mobile devicesthat are connected to access point 176. The mobile devices receiving theinformation can use the information to determine their geographiclocations. The system can divide a three-dimensional geographic spaceinto three-dimensional grid 170. Three-dimensional grid 170 can becomposed of three-dimensional cells 172. Each three-dimensional cell 172can have a projection to a two-dimensional area that corresponds to cell152 of geographic grid 150. Each three-dimensional cell 172 can have aheight (e.g., measured in meters) as a dimension. Presence space 174 canbe referred to as being located in cell 172 if the center of presencespace 174 is in cell 172. The system can limit the number of presencespaces in cell 172 based on a popularity of the presence space (e.g.,how many connections are made from mobile devices 158 in presence spaceto access point 176), a stability of presence space 174 (e.g., howstable presence space 174 has been), a longevity of access point 176(e.g., how long access point 176 has existed), and a freshness ofpresence space 174 (e.g., when was a latest location transmission frommobile device 158 connected to access point 176 was received).

The system can transmit information on presence space 174 andneighboring presence spaces based on three-dimensional cells 172 ofthree-dimensional grid 170 to a mobile device (e.g., mobile device 160)that is connected to access point 176. Mobile device 160 can use theinformation to estimate a current location of mobile device 160 in thethree-dimensional space, and display the estimated current location on athree-dimensional map.

Exemplary Server-Side Process and System for Determining Locations ofWireless Access Points

FIGS. 3A-3C illustrate exemplary stages of determining locations ofwireless access points. For convenience, the techniques will bedescribed in reference to a system that includes a server thatimplements the techniques.

FIG. 3A illustrates an exemplary stage of a multi-pass analysis that canbe used to determine a presence area associated with access point 155.Access point 155 can have a coverage area 202, which can be determinedby a signal strength of a transmitter of access point 155 and otherfactors (e.g., physical characteristics of geographic areas surroundingaccess point 155). Mobile devices 158 that are located within coveragearea 202 can wirelessly connect to access point 155. Access point 155can allow mobile devices 158 to connect to a wired network throughvarious gateways. The wired network can include a data network (e.g.,the Internet), a public switched telephone network (PSTN), other digitalor analog networks, or a combination of the above.

Mobile device 158 can include location-aware mobile devices (e.g.,GPS-enabled mobile devices). Each location-aware mobile devices 158(represented as black triangle of FIG. 3A) can detect its currentgeographic location. The current geographic location can be representedby geographic coordinates that include a latitude and a longitude ofmobile device 158. When mobile devices 158 communicate with access point155, mobile devices 158 can transmit location information to the systemthrough access point 155. The location information can be associatedwith an identifier of access point 155 (e.g., a Media Access Control(MAC) address of access point 155). The system can use the locationinformation received from multiple mobile devices 158 to determine thepresence area that can be associated with access point 155. The presencearea does not necessarily enclose a location where access point 150 isactually located. Neither is it necessary for the presence area tocorrespond to the geometric location or shape of coverage area 202,although the presence area can be located within coverage area 202.

Distribution of mobile devices 158 with coverage area 202 can correspondto a snapshot of mobile devices 158 at a particular time (e.g., 8:30 amlocal time for a time zone in which access point 155 is located). Eachmobile device 158 can be associated with a single location. Distributionof mobile devices 158 with coverage area 202 can also correspond tolocations of mobile devices 158 over a period of time (e.g., six hoursfrom 4 am to 10 am). Each mobile device 158 can be associated withmultiple locations (e.g., when mobile device 158 is moving). A singlemobile device 158 that is associated with multiple locations can berepresented by multiple locations in the system, as illustrated bymultiple triangles in FIG. 3A.

The server can determine an average geographic location of a set oflocations received from mobile devices 158. The set of locations caninclude locations received from mobile devices 158 at a particular timeor during a particular time period. The average geographic location canbe designated as center 244 a of circle 204 a. Center 244 a of circle204 a need not coincide with the location of an access point (e.g.,access point 155 or access point 200). The server can calculate adistance between the average geographic location and each location inthe set and identify one or more outliers. Outliers can be locations inthe set that are located the farthest from the average geographiclocation. Outliers (e.g., location 210) whose distances to the centerexceed a threshold can be excluded from the set. Circle 204 a can haveradius 245 a that corresponds to the longest distance between theaverage geographic location and locations in a current set after theoutliers are excluded.

FIG. 3B illustrates an exemplary stage of the multi-pass analysissubsequent to the stage of FIG. 3A. Locations whose distances to theaverage geographic location of FIG. 3A (center 244 a of circle 204 a)exceed a threshold have been excluded from the set. The threshold can beconfigured such that a percentage of positions (e.g., five percent oflocations of FIG. 3A) are excluded. A new average geographic locationcan be calculated based on the locations remaining in the set (e.g., the95 percent of locations remaining). The new average geographic locationcan be, for example, center 244 b of circle 204 b. In variousimplementations, calculating the new average geographic location caninclude averaging the remaining locations in the set, selecting a mediumgeographic location in the set (e.g., by selecting a medium latitude ora medium longitude), or applying other algorithms. Algorithms forcalculating the average geographic location can be identical in eachpass of the multi-pass analysis, or be distinct from each other in eachpass.

Area encompassed by circle 204 b can be smaller than the areaencompassed by circle 204 a as determined in a prior pass when outlierlocations are excluded. The smaller area can reflect an increasedprecision of the calculation. Center 244 b of circle 204 b does notnecessarily coincide with center 244 a of circle 204 a. In someimplementations, radius 245 b of circle 204 b can correspond to aremaining location of mobile device 158 that is farthest away fromcenter 244 b of circle 204 b. The radius can represent an error marginof the new estimation the presence area calculated in the current pass.

FIG. 3C illustrates an exemplary final stage of the multi-pass analysis.When certain exit conditions are satisfied, the system can terminate theiterative process after the final stage. The final stage can produce afinal average geographic location that corresponds to a cluster ofpositions of mobile devices 158. The final average geographic locationcan be represented as center 244 c of circle 204 c. Circle 204 c canhave radius 245 c that corresponds to a final error margin, which isbased on a distance between the final average geographic location and alocation in the cluster. Circle 204 c can be designated as the presencearea associated with access point 155 through and identifier (e.g., aMAC address) of access point 155.

The server can determine whether to include the identifier of accesspoint 155 and associated presence area in a location database based onvarious factors. For example, the server can count the number ofpresence areas in cell 152 of geographic grid 150, and select a numberof presence areas based on popularity, stability, and longevity. Theserver can send information of the presence areas (including presencearea 204 c if presence area 204 c is selected) in the location databaseto a mobile device (e.g., mobile device 215), regardless whether mobiledevice 215 is GPS-enabled.

FIG. 3D illustrates an exemplary stage of determining locations ofwireless access points in a three-dimensional space. In FIG. 3D, axes X,Y, and Z can be used to indicate the three-dimensional space. Forexample, axes X, Y, and Z can represent longitude, latitude, andaltitude, respectively. For convenience, location of access point 176 isshown to coincide with point zero on the X, Y, and Z axes in FIG. 3D. Insome implementations, an actual location (e.g., latitude, longitude, andaltitude coordinates) of access point 176 is optional in thecalculations.

Each triangle of FIG. 3D can represent a location of a mobile devicelocated in the three-dimensional space. The locations can haveprojections (e.g., projection 226) on a plane in the three-dimensionalspace. The plane can be defined at arbitrary altitude (e.g., thealtitude of access point 176). For example, the plane can be defined byaxes X and Y. Access point 176 can correspond to a coverage space 222,which can be determined by signal strength of access point 176 and otherlimiting factors (e.g., floors, ceilings, buildings in signal path).

A multi-pass analysis can associate a geographic space with access point176 of a WLAN based on a set of locations received from location-awaremobile devices 158 that are located in cell space 202. In a pass of themulti-path analysis, an average geographic location (e.g., center ofspace 224) can be determined by, for example, averaging the latitudes,longitudes, and altitudes coordinates of locations in the set. Distancesbetween the average geographic location and locations in coverage space222 can be calculated. Locations that are within coverage space 222 butare sufficiently far away from the average geographic location can beexcluded from the set and from further computations. A radius of space224 can be determined by, for example, the farthest distance betweenremaining locations in the set and the average geographic location.

The system can repeat the stages of calculating an average geographiclocation in a set, calculating distances between the average geographiclocation and the locations in the set, and excluding from the setlocations based on the calculated distances. The repetition can continueuntil an exit condition is satisfied. A space having a center at theaverage geographic location and a radius that is based on a distancebetween the average geographic location and a remaining location in theset can be designated as a presence space that can be associated withaccess point 176.

FIG. 4A is a flowchart illustrating exemplary process 300 of determininglocations of wireless access points. Process 300 can be used, forexample, to determine a presence area or presence space associated withan access point of the WLAN. The presence area or presence space can beused to determine a location of a non-GPS-enabled mobile device. Forconvenience, process 300 will be described in reference to a system thatimplements process 300.

The system can receive (302) a set of locations from one or more firstmobile devices 158 connected to access point 155. Each location can berepresented by a set of geographic coordinates (e.g., a latitude, alongitude, and an altitude). The location can be associated with anidentifier (e.g., a MAC address) of access point 155. The identifier ofaccess point can be automatically supplied by access point 155 whenaccess point 155 communicates with the system. In variousimplementations, the set of locations can correspond to a period of time(e.g., 6 hours, or from 6 am to 10 am of a time zone in which accesspoint 155 is located).

In some implementations, the period of time can be configured to reflectcharacteristics of specific usage patterns at various hours of a day. Anarea where mobile devices connected to access point 155 are most likelylocated can vary during the day, indicating various usage patterns inspecific hours. For example, the period of time can correspond to“commute time,” “business hours,” “night time,” etc. The characteristicsof the time of the day can correspond to various usage patterns ofmobile devices 158. For example, during commute time, the presence areaassociated with access point 155 can be at or near a freeway; duringbusiness hours, the presence area associated with access point 155 canbe at or near an office building; at nighttime, the presence areaassociated with access point 155 can spread out without a particularpoint of concentration. The system can calculate the presence area basedon locations received, for example, from 4 am to 10 am, and recalculatethe presence area based on location received from 10 am to 4 pm, etc.Locations received in each characteristic time period can be groupedinto a set in the system. The locations can be stored in any datastructure (e.g., set, list, array, data records in a relationaldatabase, etc.) on a storage device coupled to the server.

The system can determine (304) a geographic location associated withaccess point 155 based on an average of the received set of locations.The geographic location can include a presence area or a presence spaceas described above. The presence area or presence space can beassociated with access point 155 by, for example, the MAC address ofaccess point 155. In some implementations, determining the geographiclocation can include applying a multi-pass algorithm on the received setof locations, including excluding at least one location from the set ineach pass. Determining the geographic location can include applying themulti-pass algorithm periodically.

The system can assign (306) access point 155 and the geographic locationassociated with access point 155 to a cell (e.g., cell 152) on ageographic grid (e.g., geographic grid 150) based on various factorsincluding popularity of access point 155, stability of the geographiclocation, and longevity of access point 155. In some implementations,popularity of access point 155 can measure how many mobile devices 158are connected to access point 155. Popularity of access point can bemeasured by, for example, how many locations of mobile devices 158 thatare connected to access point 155 are received in a period of time bythe system.

Stability of the presence area associated with access point 155 canreflect how reliable the presence area is, if the presence area is usedfor estimating a location of a device connected to access point 155.Stability of the presence area associated with access point 155 can bemeasured by, for example, comparing the presence areas calculated by thelast two calculations, and determine a degree of overlap between thepresence areas. The higher the degree of overlap, the more stable thepresence area.

Longevity of access point 155 can reflect the quality of the dataassociated with access point 155. For example, an access point that hasbeen in the database for a longer time can be more reliable than anaccess point that has been recently added. Longevity of access point 155can be measured by a history of data in a location database.

In some implementations, a freshness of data can also be used todetermine whether the presence area associated with access point 155will be assigned to cell 152 of geographic grid 150. The freshness ofdata can be measured by how long ago the system received the most recentlocation from mobile device 158.

The system can rank each presence area located in cell 152 of geographicgrid 150 based on the popularity, stability, longevity, and freshness.At least a portion of all the presence areas located in cell 152 (e.g.,three presence areas, including the presence area that is associatedwith access point 155) can be assigned to cell 152. Assigned accesspoints and presence areas can be used for locating mobile devices (e.g.,mobile devices 160) that are connected to access point 155. Unassignedpresence areas can be stored in the location database for future use.

The system can provide (308) the geographic location associated withaccess point 155 to a second mobile device (e.g., mobile device 160)that is connected to access point 155. The system can further provideother geographic locations located in the same cell, as well asgeographic locations associated with access points assigned toneighboring cells to the second mobile device. The locations can betransmitted from access point 155 to the second mobile device uponrequest or using various push or broadcast technologies.

In some implementations, the system can receive, process, and transmitthree-dimensional location information. Presence spaces (e.g., presencespace 174) can be assigned to three-dimensional cells (e.g.,three-dimensional cell 172) on a geographic three-dimensional grid(e.g., three-dimensional grid 170). The locations can be transmittedfrom access point 176 to a second mobile device that is connected toaccess point 176 upon request or using various push or broadcasttechnologies.

FIG. 4B is a flowchart illustrating an exemplary process 304 ofcalculating an average geographic location using a set of locations. Forconvenience, process 304 will be described in reference to a system thatimplements process 304.

The system can calculate (324) an average geographic location using thelocations in the set. Calculating the average geographic location caninclude calculating an average of latitudes, longitudes, and altitudesof the locations in the set, and designating a position at thecalculated average latitude, longitude, and altitude as the averagegeographic location. In some implementations, calculating the averagegeographic location can include designating a position at a medianlatitude, median longitude, and median altitude of the positions in theset as the average geographic location.

The system can calculate (326) distances between the locations in theset and the average geographic location. In some implementations, thesystem can calculate a linear distance between each of the locations inthe set and the average geographic location in Euclid space. In someimplementations, the system can calculate a geodesic distance betweeneach of the locations in the set and the average geographic location,taking curvature of the earth into consideration.

The distances calculated in stage 326 can be designated as a radiusassociated with a center. The center can be the average geographiclocation calculated in stage 324, which can be a center (e.g., center244 a) of a circle (e.g., circle 204 a). The radius (e.g., radius 245 a)of the circle can be determined based on at least one distance between alocation in the set of locations and the average geographic location. Insome implementations, the radius can equal to the longest distancebetween the average geographic location and a location remaining in theset. In some implementations, the radius can be a distance that, whencircle 106 d is drawn using the radius and the average geographiclocation as a center, the circle can enclose a percentage (e.g., 80percent) of the locations remaining in the set. The radius can representa margin of error beyond which an estimation of a location of anon-GPS-enabled mobile device is less likely to be statisticallymeaningful.

The system can exclude (328) from the set at least one location based ona distance between the average location and the location. In someimplementations, the system can exclude locations whose distance to theaverage geographic location exceeds a threshold distance. In each passof the multi-pass analysis, the system can increase a precision of theestimated average geographic location by excluding locations that appearto be away from a concentration of locations (e.g., a cluster). Alocation that is away from a cluster of locations can be less useful inestimating the presence area associated with access point 155, and canbe excluded. In various implementations, the threshold distance can varyfrom one pass to a next pass. In some implementations, the thresholddistance can be a distance to the average geographic location withinwhich a certain percentage (e.g., 95 percent) of locations in the setare located. In some implementations, the threshold distance can be aset of distances corresponding to the passes (e.g., 250 meters for thefirst pass, 150 meters for the second pass, etc.). The system canexclude at least one location from the set when the distance between theaverage geographic location and the location exceeds the thresholddistance.

The system can repeat stages 324, 326, and 328 of process 304 until anexit condition is satisfied. The system can determine (330) whether anexit condition is satisfied for terminating the repetition. In someimplementations, the exit condition can be satisfied when a number ofrepetitions reach a threshold number (e.g., 10 times). The thresholdnumber, as well as the percentage of locations to exclude, can beconfigurable to fine tune a balance between certainty (e.g., a largerpresence area can result in more confidence that a mobile device in thecell is actually located in the presence area) and precision (e.g., asmaller presence area can result in more accurate location of a mobiledevice). For example, when the percentage is set to 95 percent and thenumber of passes is set to 10, the final pass can produce a circle thatencompasses about 60 percent of all location data points.

In some implementations, the exit condition of stage 330 can besatisfied when the presence area or presence space is sufficientlysmall. In cells where mobile devices are highly concentrated, a presencearea can be sufficiently small that further passes will not necessarilyincrease the precision. The repetition of stages 324, 326, and 328 canterminate when the radius of the circle reaches below a thresholdradius. For example, the threshold radius can be 8-10 meters. Thethreshold radius can differ from access point to access point, based onthe distribution pattern of the locations in the set received (e.g.,number of location data points received, density of the location datapoints, and concentration areas in the cells).

The system can designate (332) the geographic area as a circle havingthe average geographic location as a center and a radius based on atleast one calculated distance. The geographic area can be associatedwith an access point (e.g., access point 155). The server can providethe geographic area (e.g., the center and radius) for displaying on amap display of a mobile device. The center can be represented inlatitudes and longitudes. In some implementations where distances arecalculated in three-dimensional spaces, the center can further berepresented in an altitude.

FIG. 4C is a block diagram illustrating an exemplary system implementingtechniques of determining locations of wireless access points. Thesystem can include one or more processors, one or more memory devicesstoring instructions, and other hardware or software components. Thesystem can include location engine 350 that can be used to determine apresence area or presence space to be associated with an access point(e.g., access point 155).

Location engine 350 can include data collection module 352 that canreceive data from various mobile devices through various access points.The data can include multiple data points that can indicate locations ofone or more location-aware mobile devices (e.g., mobile devices 158) aswell as identifiers of access points (e.g., MAC addresses of accesspoints 155) indicating to which access point mobile devices 158 areconnected. In some implementations, the data points can also includeinformation on which time zone mobile devices 158 are located. Datacollection module 352 can include data reception module 354, which canreceive data transmitted from mobile devices 158 and data indexingmodule 356. Data indexing module 356 can perform various processing onthe received data points. For example, data indexing module 356 can sortlatitudes, longitudes, and altitudes based on cell IDs. Data indexingmodule 356 can also group data into sets based on time periods. Forexample, a new set of received locations can be created for aconfigurable period of time (e.g., six hours).

Sets of received locations of mobile devices 158 can be stored in datapoint database 360. Data point database 360 can store current andhistorical locations of various mobile devices 158. Data point database360 can include an ad hoc database, relational database, and/orobject-oriented database. Data point database 360 can be hosted locallyor remotely in relation to location engine 350.

Location calculation module 364 can be utilized to calculate an averagegeographic location in sets of data points in data points database 360,calculate distances between the average geographic location andlocations of various data points, and exclude locations from the setsfor further computation. Location calculation module 364 can perform thecalculations for a particular set (e.g., a set of data points associatedwith a cell ID) until an exit condition is reached for the particularset. Location calculation module 364 can determine presence areas orpresence spaces for each access point (e.g., access point 155)

In some implementations, location calculation module 464 can performvalidity checks on the presence areas or presence spaces based onvarious criteria and various data in the data points using validitychecker 366. For example, the data points received from mobile devices158 can include Mobile Country Codes (MCCs) and time zone information.Validity checker 366 can compare a calculated presence area or presencespace with polygons corresponding to countries represented by the MCCsand polygons corresponding to the time zones. If a calculated presencearea or presence space is located outside the polygons, validity checker366 can register an anomaly and remove the access point.

Location filtering engine 368 can determine whether a presence area orpresence space can be used to estimate a location of a mobile devicethat is currently connected to an access point. Location filteringengine 368 can divide a geographic region into cells 152 of geographicgrid 150, or three-dimensional cells 172 of three-dimensional grid 170.Location filtering engine 368 can rank presence areas or presence spacesbased on popularity, stability, longevity, and freshness. Locationfiltering engine 368 can assign the top-ranked presence areas orpresence spaces located in each cell 152 or three-dimensional cell 172to cell 152 or three-dimensional cells.

Presence areas and presence spaces can be defined by a center having theaverage latitude, longitude, and altitude coordinates of the set oflocations. Presence areas and presence spaces can be further defined bya radius determined based on distances from locations in the set oflocations to the center. The latitude, longitude, and altitudecoordinates of centers for the presence areas and presence spaces andthe radii of the presence areas and presence spaces can be stored inlocation database 372. Location database 372 can store both assigned andunassigned presence areas and presence spaces. Unassigned presence areasor presence spaces can be assigned in subsequent calculations bylocation calculation module 364. Location database 372 can be updatedperiodically by location calculation module 364.

The data of location database 372 can be distributed to mobile devicesusing data distribution module 376. Data distribution module 376 cansend information of assigned presence areas and presence spaces (e.g.,center coordinates and radii) that is associated with access points tomobile devices (e.g., non-GPS-enabled mobile device 160) upon request,through broadcasting, or using various push technology without receivingrequests from the mobile devices.

In some implementations, data distribution module 376 can send multiplepresence areas and presence spaces to mobile devices in one transmissionsession. To reduce the number of location transmissions to the mobiledevices that can consume communication bandwidths of the mobile device,data distribution module 376 can use neighbor locator 378 to locatecells that are neighbors of the cell in which mobile device 160 islocated. Neighboring cells can include, for example, a number of cellssurrounding the cell in which mobile device 160 is located such that thetotal area of the cell and the surrounding cells cover a certaingeographic area (e.g., one or two squire kilometers). Sendinginformation on presence areas and presence spaces associated withmultiple cells (e.g., 400 cells) to mobile device 160 can reduce thenumber of transmissions when mobile device 160 moves across cells. Insuch implementations, data distribution module 376 only needs to send anupdate to mobile device 160 when mobile device 160 moves out of allcells previously sent.

Determining Locations of Mobile Devices Using Locations Filtering

FIG. 5A illustrates techniques for determining locations of mobiledevices using locations of wireless access points. Mobile device 400 canbe an exemplary mobile device that can use locations of wireless accesspoints to determine its location. An exemplary section of acommunication network that includes access points 400 is illustrated.

Mobile device 400 can be wirelessly connected to access point 404 a.From access point 404 a, mobile device 400 can receive data that includeinformation on presence areas or presence spaces (including presenceareas 406) of neighboring access points. Mobile device 400 can store thereceived data on a storage device. The stored data can be updatedperiodically.

In the example shown, mobile device 400 is connected to access point 400a. In addition, mobile device 400 is within communication ranges toaccess points 404 b, 404 c, and 404 d. Mobile devices 400 can identifyaccess points 404 a, 404 b, 404 c, and 404 d under wirelesscommunication protocols used in the WLAN (e.g., IEEE 802.11a). Accesspoints 404 a, 404 b, 404 c, and 404 d can be identified by MAC addressesof the access points or other identifiers (e.g., Bluetooth™identifiers).

Mobile device 400 can identify presence areas 406 a, 406 b, 406 c, and406 d that are associated with access points 404 a-d, respectively.Identifying presence areas 406 a-d can include retrieving information onthe presence areas 406 a-d from a memory device coupled to mobile device400. In some implementations, mobile device 400 can request from aserver the presence areas 406 a-d by sending to the server identifiersof access points 404 a-d.

Based on presence areas 406 a-d, mobile device 400 can execute aniterative process (e.g., a multi-pass analysis) on the presence areas406 a-d. The iterative process can produce geographic area 402, whichcan be an estimate of mobile device 400's current geographic location.Geographic area 402 can be a geographic space when three-dimensionallocation information is utilized. Mobile device 400 can display theestimated current location on a display device (e.g., on a map display).

FIG. 5B is a flowchart illustrating exemplary process 410 of locationfiltering using mobile country code. For convenience, process 410 willbe described in reference to mobile device 400 that implements process410.

Mobile device 400 can wirelessly receive (412) identifiers of one ormore access points 404 and a current MCC. The identifiers (e.g., MACaddresses) of access points 404 can be received from the access points.Access points can have overlapping coverage areas. For example, mobiledevice 400 can be located within a communication range of multipleaccess points (e.g., access points 404). The MCC can be received from atransceiver (e.g., a cell tower) of a cellular communications network.

Mobile device 400 can identify (414) a polygon that is a bounding box ofa geographic area that corresponds to the current MCC. The geographicarea can correspond to a country or a portion of a country (e.g.,Alaska). The polygon can be defined by latitude and longitudecoordinates of extreme points of the geographic area. The polygon can beidentified from a geographic database storing the polygon in associationwith the MCC. The geographic database can be a database local to mobiledevice 400. For example, mobile device 400 can store in a localgeographic database the polygons that are bounding boxes of geographicareas identified by MCCs. The geographic database can also be storedremotely (e.g., on a remotely-located server computer). The geographicdatabase can be pre-populated by a server and installed on (e.g.,downloaded to) mobile device 400.

In some implementations, polygons of countries can further be associatedwith time zones, which can extend MCC based location filtering. Thepolygon can be further be defined by time zones within a country. Thepolygon can be identified by MCC in combination with a current timezone. For example, bounding boxes 102 a-c can be associated with MCCs310-316 (United States). Bounding box 102 a can be further associatedwith Alaska time zone (Greenwich Mean Time (GMT) minus nine hours forstandard time). Bounding box 102 b can be further divided to foursub-boxes, each sub-box corresponding to Eastern Time Zone (GMT minusfive hours), Central Time Zone (GMT minus six hours), Mountain Time Zone(GMT minus seven hours), and Pacific Time Zone (GMT minus eight hours).Bounding box 102 c can further be associated with Hawaii/Aleutian timezone (GMT minus 10 hours).

Mobile device 400 can receive from a cell tower an encoded current timezone. A communications and controls processor (e.g., a basebandprocessor) of mobile device 400 can decode the received current timezone. From the MCC and current time zone, mobile device 400 can identifya sub-bounding box. If mobile device 400 detects that a location of anaccess point to which mobile device 400 is connected is outside thesub-bounding box, the mobile device can filter out that access point.For example, if mobile device 400 has determined that a current MCC is“310” (United States of America), mobile device 400 can identify bindingboxes 102. When mobile device 400 determines that the current time zoneis GMT minus 10 hours, mobile device can determine that the bounding boxis 102 c. Mobile device 400 can use bounding box 102 c for subsequentcalculations.

Mobile device 400 can select (416) a set of access point locations froma location database using the received access point identifiers. Alocation can be selected if the location is inside the identifiedpolygon. The location database can include identifiers of access points(e.g., MAC addresses) and corresponding geographic coordinates of theaccess points. The location database can be stored on mobile device 400.For example, mobile device can include a set of pre-determined locationsof access points (e.g., access points at or near airports). The locationdatabase can be updated periodically from a server. The locationdatabase can be updated, for example, when the server detects a movementof an access point. Location records corresponding tocurrently-connected access points that are outside the polygoncorresponding to the current MCC and time zone can be excluded from thelocation database and from further calculations.

Mobile device 400 can determine (418) a current location of mobiledevice 400 based on an average location of the selected set of accesspoint locations. Determining the current location can include applyingan adaptive location calculation process to the set of access pointlocations, which have already been filtered using the MCC and time zone.Further details of determining the current location, including theadaptive location calculation process, will be described below infurther detail with respect to FIG. 5C. Mobile device 400 can displaythe current location on a map display of the mobile device.

FIG. 5C is a flowchart illustrating exemplary process 418 of determininga location of a mobile device using locations of wireless access points.For convenience, process 418 will be described in reference to mobiledevice 400 that implements process 418.

The location database can include identifiers of access points (e.g.,access points 404) of a wireless communication network (e.g., a WLAN)and a set of locations associated with the access points. The set oflocations can correspond to presence areas 406 or presences spacesassociated with the access point. Each location can be represented bygeographic coordinates (e.g., latitude, longitude, and altitude). Eachlocation can be associated with an identifier (e.g., a MAC address) ofan access point 404. In various implementations, the set of locations bereceived from a server periodically or upon request.

Mobile device 400 can calculate (434) an average geographic locationusing the locations in the set. Calculating the average geographiclocation can include calculating an average of latitudes, longitudes,and altitudes of the locations in the set, and designating a position atthe calculated average latitude, longitude, and altitude as the averagegeographic location. In some implementations, calculating the averagegeographic location can include designating a location at a medianlatitude, median longitude, and median altitude of the positions in theset as the average geographic location.

Mobile device 400 can calculate (436) distances between the locations inthe set and the average geographic location. In some implementations,the system can calculate a linear distance between each of the locationsin the set and the average geographic location in Euclid space. In someimplementations, the system can calculate a geodesic distance betweeneach of the locations in the set and the average geographic location,taking curvature of the earth into consideration.

The distances calculated in stage 436 can be designated as a radiusassociated with a center. The center can be the average geographiclocation calculated in stage 434, which can be a center of a circle(e.g., circle surrounding geographic area 402). The radius of the circlecan be determined based on at least one distance between a location inthe set of locations and the average geographic location. In someimplementations, the radius can equal to the longest distance betweenthe average geographic location and a location remaining in the set. Insome implementations, the radius can be a distance that, when a circleis drawn using the radius and the average geographic location as acenter, the circle can enclose a percentage (e.g., 80 percent) of thelocations remaining in the set. The radius can represent a margin oferror beyond which an estimation of a location of a non-GPS-enabledmobile device is less likely to be statistically meaningful.

Mobile device 400 can exclude (438) from the set at least one locationbased on a distance between the average location and the location. Insome implementations, the system can exclude locations whose distance tothe average geographic location exceeds a threshold distance. In eachpass of the multi-pass analysis, the system can increase a precision ofthe estimated average geographic location by excluding locations thatappear to be away from a concentration of locations (e.g., a cluster). Alocation that is away from a cluster of locations can be less useful inestimating a current location of mobile device 400, and can be excluded.In various implementations, the threshold distance can vary from onepass to a next pass. In some implementations, the threshold distance canbe a distance to the average geographic location within which a certainpercentage (e.g., 95 percent) of locations in the set are located. Insome implementations, the threshold distance can be a set of distancescorresponding to the passes (e.g., 50 meters for the first pass, 30meters for the second pass, etc.). The system can exclude at least onelocation from the set when the distance between the average geographiclocation and the location exceeds the threshold distance.

Mobile device 400 can repeat stages 434, 436, and 438 of process 430until an exit condition is satisfied. The system can determine (440)whether an exit condition is satisfied for terminating the repetition.In some implementations, the exit condition can be satisfied when anumber of repetitions reach a threshold number (e.g., five times). Thethreshold number can relate to a number of locations in the originallyreceived set. The threshold number, as well as the percentage oflocations to exclude, can be configurable to fine tune a balance betweencertainty (e.g., a larger presence area can result in more confidencethat a mobile device in the cell is actually located in the presencearea) and precision (e.g., a smaller presence area can result in moreaccurate location of a mobile device). For example, when the percentageis set to 95 percent and the number of passes is set to 10, the finalpass can produce a circle that encompasses about 60 percent of alllocation data points.

In some implementations, the exit condition of stage 330 can besatisfied when the presence area or presence space is sufficientlysmall. In areas where access points 404 are highly concentrated, anestimated current location can include an area sufficiently small thatfurther passes will not necessarily increase the precision. Therepetition of stages 434, 436, and 438 can terminate when the radius ofthe circle reaches below a threshold radius. For example, the thresholdradius can be 8-10 meters. The threshold radius can be based on radii ofpresence areas 406. In some implementations, if some radii of presenceareas 406 are sufficiently small, the threshold radius can be small, toreflect a confidence on the estimate.

Mobile device 400 can display (442) the current location of mobiledevice 400 using a circle having the average geographic location as acenter and a radius based on at least one calculated distance. Thecenter can be represented in latitudes and longitudes. In someimplementations where distances are calculated in three-dimensionalspaces, the center can further be represented in an altitude. In someimplementations, mobile device can further display the current locationon a display device on a map user interface. Exemplary map userinterfaces will be described below in reference to FIG. 6.

Exemplary User Interfaces for Determining Locations of Mobile Devices

FIG. 6 illustrates an exemplary user interface for determining locationsof mobile devices using locations of wireless access points. In FIG. 6,an exemplary map (map 502) with a geographic area is displayed on mobiledevice 500. In some implementations, mobile device 500 can display themap 502 on the touch sensitive display 530 of mobile device 500. The map502 can be displayed when a user selects the maps object 144 to viewmapping and location based services. In some implementations, objects,such as the maps object 144, can be selected by voice activation. Asearch bar 504 and a bookmarks list object 506 can be displayed at thetop of the map 502. Below the bottom of the map one or more displayobjects can be displayed, for example a search object 508, a directionsobject 510, a map view object 512, and a current location object 514.

The search bar 504 can be used to find an address or other location onthe map. For example, a user can enter their home address in the searchbar 504, and the region containing the address would be displayed on themap 502. The bookmarks list object 506 can, for example, bring up aBookmarks list that contains addresses that are frequently visited, suchas a user's home address. The Bookmarks list can also, for example,contain special bookmarks such as the current location (e.g. thecurrent, location of mobile device 500).

The search object 508 can be used to display the search bar 504 andother map related search menus. The directions object 510 can, forexample, bring up a menu interface that allows the user to enter a startand end location. The interface can then display information (e.g.,directions and travel time for a route from the start location to theend location). The map view object 512 can bring up a menu that willallow the user to select display options for the map 502. For example,the map 502 can be changed from black and white to color, the backgroundof the map can be changed, or the user can change the brightness of themap.

The current location object 514 can allow the user to see a geographicarea 516 on the map 502 indicating where the device 150 is currentlylocated. Geographic area 516 can correspond to an estimated geographicarea (e.g., geographic area 402) whose center is an average geographiclocation of data points associated with access points that are withincommunication range of mobile device 500. Radius of geographic area 516can be determined based on a distance between the average geographiclocation and one or more locations associated with the access points. Aspecial current location bookmark can be placed in the Bookmarks listwhen the current location object 514 is selected. If the special currentlocation bookmark was previously set in the Bookmarks list, the oldbookmark information can, for example, be replaced with the new currentlocation information. In some implementations, the special currentlocation bookmark is tied to the centroid of geographic area 516. Thatis, the special current location bookmark can include the coordinatesfor the centroid of the geographic area 516. The geographic area 516 canbe based on location data determined or estimated using locationinstructions stored in a memory device of mobile device 500. Thegeographic area 516 can, for example, be depicted by a circle,rectangle, square, hexagon, or other enclosed region with crosshairs, orsome other distinctive element to differentiate the geographic area 516from the map 502.

In some implementations, geographic area 516 can indicate a region inwhich mobile device 500 is determined or estimated to be located, andthe geographic area may not necessarily be centered on the actualcurrent position of mobile device 500. In this example, mobile device500 may be located off-center within the geographic area. In anotherexample, geographic area 516 can be centered on an estimated currentposition of mobile device 500.

Mobile device 500 can, for example, center the map view on thegeographic area 516 when the current location object 514 is tapped orotherwise selected. In some implementations, the zoom level of the mapcan be adjusted based on the accuracy or precision of the location dataor the technology, system, or service that provided the location data.For example, the map can be zoomed out when mobile device 500 cannotreceive GPS signals for lower accuracy and uses access point data todetermine its location. The map can be zoomed in for higher accuracy ifmobile device 500 is capable of using GPS location data to determine itscurrent location. In some implementations, the zoom level can be basedon the velocity of mobile device 500 (e.g., the map can be zoomed out athigher velocities and zoomed in when mobile device 500 is not moving). Acombination of accuracy or precision and velocity can also be used.

If all methods for retrieving location-based data fail (e.g., whenmobile device 500 is not within communication range of any access point,or when validity checker 366 determines that no presence area can beassociated with any access points where mobile device 500 can beconnected), and there are no other systems or services available fordetermining or estimating the current position of mobile device 500, anerror can be displayed to the user and no geographic area is displayedon the map 502. The error can, for example, contain a message to theuser informing them of the failure and the possible reason or reasonsfor the failure.

Current location object 514 can be selected, for example, to activatethe estimating and displaying of geographic area 516 on map 502, to getdirections to or from the estimated current location (i.e., the centroidof geographic area 516), to send the estimated current location ofmobile device 500 to a friend (e.g., such that the friend can go to thesame location), or to create a bookmark for the estimated currentlocation.

Exemplary Mobile Device Architecture

FIG. 7 is a block diagram of an exemplary architecture 700 of a mobiledevice. The Mobile device can be, for example, a handheld computer, apersonal digital assistant, a cellular telephone, an electronic tablet,a network appliance, a camera, a smart phone, an enhanced general packetradio service (EGPRS) mobile phone, a network base station, a mediaplayer, a navigation device, an email device, a game console, or acombination of any two or more of these data processing devices or otherdata processing devices.

The mobile device can include a memory interface 702, one or more dataprocessors, image processors and/or central processing units 704, and aperipherals interface 706. The memory interface 702, the one or moreprocessors 704 and/or the peripherals interface 706 can be separatecomponents or can be integrated in one or more integrated circuits. Thevarious components in the mobile device 150 can be coupled by one ormore communication buses or signal lines.

Sensors, devices, and subsystems can be coupled to peripherals interface706 to facilitate multiple functionalities. For example, motion sensor710, light sensor 712, and proximity sensor 714 can be coupled toperipherals interface 706 to facilitate orientation, lighting, andproximity functions of the mobile device. Location processor 715 (e.g.,GPS receiver) can be connected to peripherals interface 706 to providegeopositioning. Electronic magnetometer 716 (e.g., an integrated circuitchip) can also be connected to peripherals interface 706 to provide datathat can be used to determine the direction of magnetic North.

Camera subsystem 720 and an optical sensor 722, e.g., a charged coupleddevice (CCD) or a complementary metal-oxide semiconductor (CMOS) opticalsensor, can be utilized to facilitate camera functions, such asrecording photographs and video clips.

Communication functions can be facilitated through one or more wirelesscommunication subsystems 724, which can include radio frequencyreceivers and transmitters and/or optical (e.g., infrared) receivers andtransmitters. The specific design and implementation of thecommunication subsystem 724 can depend on the communication network(s)over which the mobile device is intended to operate. For example, themobile device may include communication subsystems 724 designed tooperate over a GSM network, a GPRS network, an EDGE network, a Wi-Fi orWiMax network, and a Bluetooth network. In particular, the wirelesscommunication subsystems 724 may include hosting protocols such that thedevice may be configured as a base station for other wireless devices.

Audio subsystem 726 can be coupled to a speaker 728 and a microphone 730to facilitate voice-enabled functions, such as voice recognition, voicereplication, digital recording, and telephony functions.

I/O subsystem 740 can include a touch screen controller 742 and/or otherinput controller(s) 744. Touch-screen controller 742 can be coupled to atouch screen 746 or pad. Touch screen 746 and touch screen controller742 can, for example, detect contact and movement or break thereof usingany of a plurality of touch sensitivity technologies, including but notlimited to capacitive, resistive, infrared, and surface acoustic wavetechnologies, as well as other proximity sensor arrays or other elementsfor determining one or more points of contact with touch screen 746.

Other input controller(s) 744 can be coupled to other input/controldevices 748, such as one or more buttons, rocker switches, thumb-wheel,infrared port, USB port, and/or a pointer device such as a stylus. Theone or more buttons (not shown) can include an up/down button for volumecontrol of speaker 728 and/or microphone 730.

In one implementation, a pressing of the button for a first duration maydisengage a lock of the touch screen 746; and a pressing of the buttonfor a second duration that is longer than the first duration may turnpower to the mobile device on or off. The user may be able to customizea functionality of one or more of the buttons. The touch screen 746 can,for example, also be used to implement virtual or soft buttons and/or akeyboard.

In some implementations, the mobile device can present recorded audioand/or video files, such as MP3, AAC, and MPEG files. In someimplementations, the mobile device can include the functionality of anMP3 player, such as an iPod™. The mobile device may, therefore, includea pin connector that is compatible with the iPod. Other input/output andcontrol devices can also be used.

Memory interface 702 can be coupled to memory 750. Memory 750 caninclude high-speed random access memory and/or non-volatile memory, suchas one or more magnetic disk storage devices, one or more opticalstorage devices, and/or flash memory (e.g., NAND, NOR). Memory 750 canstore operating system 752, such as Darwin, RTXC, LINUX, UNIX, OS X,WINDOWS, or an embedded operating system such as VxWorks. Operatingsystem 752 may include instructions for handling basic system servicesand for performing hardware dependent tasks. In some implementations,operating system 752 can include a kernel (e.g., UNIX kernel).

Memory 750 may also store communication instructions 754 to facilitatecommunicating with one or more additional devices, one or more computersand/or one or more servers. Memory 750 may include graphical userinterface instructions 756 to facilitate graphic user interfaceprocessing; sensor processing instructions 758 to facilitatesensor-related processing and functions; phone instructions 760 tofacilitate phone-related processes and functions; electronic messaginginstructions 762 to facilitate electronic-messaging related processesand functions; web browsing instructions 764 to facilitate webbrowsing-related processes and functions; media processing instructions766 to facilitate media processing-related processes and functions;GPS/Navigation instructions 768 to facilitate GPS and navigation-relatedprocesses and instructions; camera instructions 770 to facilitatecamera-related processes and functions; magnetometer data 772 andcalibration instructions 774 to facilitate magnetometer calibration.Memory 750 can include location instructions 776 that can be used totransmit a current location to an access point, and to determine anestimated current location based on location data associated with accesspoints to which the mobile device is within a communication range.Memory 750 can also store other software instructions (not shown), suchas security instructions, web video instructions to facilitate webvideo-related processes and functions, and/or web shopping instructionsto facilitate web shopping-related processes and functions. In someimplementations, the media processing instructions 766 are divided intoaudio processing instructions and video processing instructions tofacilitate audio processing-related processes and functions and videoprocessing-related processes and functions, respectively. An activationrecord and International Mobile Equipment Identity (IMEI) or similarhardware identifier can also be stored in memory 750.

Each of the above identified instructions and applications cancorrespond to a set of instructions for performing one or more functionsdescribed above. These instructions need not be implemented as separatesoftware programs, procedures, or modules. Memory 750 can includeadditional instructions or fewer instructions. Furthermore, variousfunctions of the mobile device can be implemented in hardware and/or insoftware, including in one or more signal processing and/or applicationspecific integrated circuits.

A number of implementations of the subject matter have been described.Nevertheless, it will be understood that various modifications can bemade without departing from the spirit and scope of the invention. Forexample, the location-aware devices are referred to as GPS-enabled.Location-aware mobile devices can also be based triangulation or othertechnology. Cells are represented as substantially rectangular in shapein the figures. The actual shape of a cell can vary. Locations aredescribed as “circles.” The term “circle” used in this specification caninclude any geometric shape (e.g., an ellipsis, a square, a convex orconcave polygon, or a free-style shape) that need not be perfectlycircular but is closed or has an appearance of an enclosure. The radiusof a geometric shape that is not perfectly circular can include anaverage distance between various points on the boundary of the geometricshape and a center of the geometric shape. WiFi and WiMax networks areused as examples. Other wireless technology (e.g., cellular network) canalso be employed. Accordingly, other implementations are within thescope of the following claims.

1. A method executed by a mobile device, comprising: receivingidentifiers of one or more access points of a wireless communicationsnetwork and a current mobile country code (MCC); identifying a polygonthat is a bounding box of a geographic area that corresponds to thecurrent MCC; selecting a set of access point locations from a locationdatabase using the received identifiers, where the access pointlocations are inside the identified polygon; and determining a currentlocation of the mobile device based on an average location of theselected set of access point locations.
 2. The method of claim 1,further comprising: storing in a geographic database polygons that arebounding boxes of geographic areas identified by mobile country codes;and storing in the location database on a storage device of the mobiledevice.
 3. The method of claim 1, further comprising: displaying thecurrent location on a map display of the mobile device.
 4. The method ofclaim 1, where the identifiers of the access points include Media AccessControl (MAC) addresses of the access points.
 5. The method of claim 1,where the polygon is defined by latitude and longitude coordinates ofpoints of the geographic area.
 6. The method of claim 1, where thegeographic area further corresponds to a time zone.
 7. The method ofclaim 1, where determining the current location comprises: (a)calculating an average geographic location using the set of access pointlocations; (b) calculating distances between the average geographiclocation and access point locations in the set; (c) excluding at leastone access point location from the set based on a distance between theaverage geographic location and the at least one location; (d) repeating(a), (b); and (c) until an exit condition is satisfied; and (e)designating a current location of the mobile device using a circlehaving the average geographic location as a center and a radius based onat least one calculated distance.
 8. The method of claim 7, where theexit condition is satisfied when a number of repetitions reaches athreshold number.
 9. The method of claim 7, where the exit condition issatisfied when the radius of the circle reaches below a threshold radius10. The method of claim 7, where each of the locations in the setincludes a latitude, and a longitude.
 11. A system, comprising: a mobiledevice configured to perform operations comprising: receivingidentifiers of one or more access points of a wireless communicationsnetwork and a current mobile country code (MCC); identifying a polygonthat is a bounding box of a geographic area that corresponds to thecurrent MCC; selecting a set of access point locations from a locationdatabase using the received identifiers, where the access pointlocations are inside the identified polygon; and determining a currentlocation of the mobile device based on an average location of theselected set of access point locations.
 12. The system of claim 11, theoperations further comprising: storing in a geographic database polygonsthat are bounding boxes of geographic areas identified by mobile countrycodes; and storing in the location database on a storage device of themobile device.
 13. The system of claim 11, the operations furthercomprising: displaying the current location on a map display of themobile device.
 14. The system of claim 11, where the identifiers of theaccess points include Media Access Control (MAC) addresses of the accesspoints.
 15. The system of claim 11, where the polygon is defined bylatitude and longitude coordinates of points of the geographic area. 16.The system of claim 11, where the geographic area further corresponds toa time zone.
 17. The system of claim 11, where determining the currentlocation comprises: (a) calculating an average geographic location usingthe set of access point locations; (b) calculating distances between theaverage geographic location and access point locations in the set; (c)excluding at least one access point location from the set based on adistance between the average geographic location and the at least onelocation; (d) repeating (a), (b), and (c) until an exit condition issatisfied; and (e) designating a current location of the mobile deviceusing a circle having the average geographic location as a center and aradius based on at least one calculated distance.
 18. The system ofclaim 17, where the exit condition is satisfied when a number ofrepetitions reaches a threshold number.
 19. The system of claim 17,where the exit condition is satisfied when the radius of the circlereaches below a threshold radius
 20. The system of claim 17, where eachof the locations in the set includes a latitude, and a longitude.
 21. Acomputer program product tangibly stored on a storage device, operableto cause a mobile device to perform operations comprising: receivingidentifiers of one or more access points of a wireless communicationsnetwork and a current mobile country code (MCC); identifying a polygonthat is a bounding box of a geographic area that corresponds to thecurrent MCC; selecting a set of access point locations from a locationdatabase using the received identifiers, where the access pointlocations are inside the identified polygon; and determining a currentlocation of the mobile device based on an average location of theselected set of access point locations.
 22. The product of claim 21, theoperations further comprising: storing in a geographic database polygonsthat are bounding boxes of geographic areas identified by mobile countrycodes; and storing in the location database on a storage device of themobile device.
 23. The product of claim 21, the operations furthercomprising: displaying the current location on a map display of themobile device.
 24. The product of claim 21, where the identifiers of theaccess points include Media Access Control (MAC) addresses of the accesspoints.
 25. The product of claim 21, where the polygon is defined bylatitude and longitude coordinates of points of the geographic area. 26.The product of claim 21, where the geographic area further correspondsto a time zone.
 27. The product of claim 21, where determining thecurrent location comprises: (a) calculating an average geographiclocation using the set of access point locations; (b) calculatingdistances between the average geographic location and access pointlocations in the set; (c) excluding at least one access point locationfrom the set based on a distance between the average geographic locationand the at least one location; (d) repeating (a), (b), and (c) until anexit condition is satisfied; and (e) designating a current location ofthe mobile device using a circle having the average geographic locationas a center and a radius based on at least one calculated distance. 28.The product of claim 27, where the exit condition is satisfied when anumber of repetitions reaches a threshold number.
 29. The product ofclaim 27, where the exit condition is satisfied when the radius of thecircle reaches below a threshold radius
 30. The product of claim 27,where each of the locations in the set includes a latitude, and alongitude.